It is rare, but 
Spirits can impregnate a human woman, with or without consent. The resulting child is a biological humanoid shaped by the spirit progenitor. All Spirit-Human Hybrids are unique, sexless, and infertile. They are almost exclusively found in 
Harmura.
These spirit hybrids can enter and leave the Spirit Realm at will, but it requires more concentration than it does for Spirits. They have abilities that are outside the normal scope of 
Trigram Magic and 
Phase Magic.